1. Field of the Invention
Off-street recreational vehicles have come of age in the United States and millions of Americans have adopted cross-country motorcycle races and dune buggy rallies as their favorite weekend pastimes. This invention relates to engine instrumentation for such off-street vehicles, and, more particularly, to a temperature gauge monitoring the condition of engine lubricating oil, providing the operator instantaneous information concerning its temperature.
Off-street vehicles generally operate in dusty and dry or muddy and wet environment during the activities with which they are used. Oftentimes, long inclines and rugged terrain require the engines to be operated in high stress modes which result in engine operating temperatures well in excess of those causing irreversible damage to engine components. The excitement and fervor of competition frequently leads the operator to ignore symptoms of these high temperature conditions and he is not made aware of the overstress condition until catastrophic failure of his machine occurs.
The device described herein provides the operator a visible, easily accessible and reliable engine temperature guage which measures the temperature of the lubricating oil and displays it on a readout dial, adjustable in orientation, for maximum visibility and utility to him.
2. Description of the Prior Art
Engine temperature monitors are old in the art. Thermocouples, pressure switches, freeze plugs and a large number of active and passive element arrays have been utilized to both monitor and control operation of internal combustion engines.
In the more common types of engine utilized for American family transportation and commercial operations, excess engine heat, unused by propulsion system elements, is carried away from sensitive engine components by liquid coolant, pumped through engine channels and cycled through radiator fins for elimination of that heat. To monitor the temperature of such engines, American auto manufacturers sometimes install simple bimetallic switches into coolant lines between the engine and its radiator, to alert the operator to overtemperature conditions by means of warning lamps or other alarms. Analog devices indicating actual degrees of coolant temperature have fallen out of favor with automobile producers but were quite common in older models which used a variety of sensors to provide stimuli to readout devices.
In motorcycles and other vehicles utilizing air cooled engines, no liquid is used to control engine temperatures and "coolant" lines are non existant. Excess heat is eliminated from these engines by means of radiating fins built into cylinder blocks and into the cylinder heads themselves. Flow of air around and over these fins transfers engine heat to the surrounding environment through convecture and radiative processes of various kinds.
It generally happens that most engine heat, for motorcycles and dune buggies, is generated when the vehicle is in a labored condition, slowed down by stresses and yet laboring for more power. Air flow over the engine, at these times, is minimal, and dangerous heat buildup occurs in engine components. This heat is transferred to as many cooler elements as possible, including the ambient air.
Principal among these cooler elements is the engine lubricating oil which is continuously cycled between its reservoir and the engine crankcase. While performing its lubricating task in the crankcase and valve sections, this oil is heated to the temperature of the engine components it lubricates and is pumped through lubricant circuits back to its reservoir.
Past patents have provided for engine lubricant monitor devices, (reference U.S. Pat. Nos. 1,399,534 (1921) and 3,693,448 (1972) but none has provided for the direct readout by an orientable indicator such as is presented herein.
Novelty and utility of the device proposed here resides in its combination of well known temperature sensor-dial readout principles with a means to allow orientation of the readout dial to a position allowing engine operators maximum visibility thereof for continuous monitoring of lubricating oil temperature.